Breast ultrasound scanning device

ABSTRACT

An apparatus and a method are disclosed for obtaining ultrasound images of a patient&#39;s breast that is chestwardly compressed with a template that is essentially planar and rotates relative to the breast while one or more ultrasound transducers moving with the template take 2D images of the breast through one or more respective radially oriented slots in the template, preferably through a membrane that is porous to a gel. The 2D images are processed into slice images representing breast slices of desired thicknesses and orientation that are displayed alone or with some of the 2D images, preferably pairs of orthogonally disposed 2D images.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application61/769,913 filed Feb. 27, 2013. This application is acontinuation-in-part of U.S. application Ser. No. 13/296,023 filed Nov.14, 2011 (which was published as US 2012/0089026 A1 and is scheduled toissue as U.S. Pat. No. 8,579,819 on Nov. 12, 2013), which is acontinuation of U.S. Application Ser. No. 11/513,481 filed Aug. 30, 2006and claiming the benefit of U.S. Provisional Application No. 60/713,282filed on Sep. 1, 2005. The entire content of all of the aboveapplications is hereby incorporated by reference herein. Alsoincorporated by reference herein are the contents of all of the patentapplications and patents and other publications cited below.

FIELD

This patent specification relates to medical imaging. More particularly,this patent specification relates to breast ultrasound imaging usingchestward compression of a breast and automated scanning with atransducer secured to a radial scanning template.

BACKGROUND

Volumetric breast ultrasound scanning usually involves a rectilinearmovement of a linear-array ultrasound transducer relative to the breasttissue of a patient, with successive scanning lines parallel to oneanother, and processing of resultant ultrasound echoes to form a datavolume representing local (e.g., voxel) values of at least one acousticproperty of the scanned breast. Volumetric ultrasound scanning of thebreast has been proposed as a complementary modality for breast cancerscreening. One example is discussed in U.S. Pat. No. 7,828,733 andinvolves using a full-field breast ultrasound (hereinafter “FFBU”)scanning apparatus that chestwardly compresses a breast, and arectilinear transducer translation mechanism that maintains anultrasound transducer in contact with the breast, as discussed, forexample, in WO 2007/014292, which employs scanning through a fabricmaterial porous to an ultrasound coupling agent and has the advantage ofreducing image artifacts such as those believed to be due to airbubbles.

One of the most important factors in breast ultrasound is image quality,which is generally defined by parameters such as image spatialresolution, signal dynamic range, and relative tissue image contrast.Image quality is very dependent on the frequency of the ultrasound.Major text books on breast ultrasound, such as “Breast Ultrasound” by A.Thomas Stavros (Publisher: Lipponcott Williams & Wilkins 2004)(hereinafter ‘Stavros 2004’) and “The Practice of Breast Ultrasound:Techniques, Findings, Differential Diagnosis” by Helmut Madjar and EllenMendelson (Publisher: Thieme 2008), counsel against using ultrasoundfrequencies below 7 to 7.5 MHz when seeking to achieve acceptable breastimages. These books explain that much higher ultrasound frequencies, ifpossible as high as 12 MHz, should be used for breast imaging.“Guidelines from IBUS (International Breast Ultrasound School) forUltrasonic Examination of the Breast” (Edited by Helmut Madjar et al;Published in European Journal of Ultrasound 1999; Vol. 9, pages 99-102)also recommends not using ultrasound frequencies below 7.5 MHz forbreast imaging. However, breast ultrasound imaging at higher frequenciespresents challenges because the ultrasound attenuation of breast tissueincreases rapidly with ultrasound frequency, as shown by D'Astous andFoster (published in Ultrasound in Med. & Biol. 1986; Vol. 12, pages795-808) (hereinafter “D'Astous and Foster”). With an attenuationcoefficient of 1 to 2 dB/cm-MHz respectively for breast cancer andparenchyma tissues, at an ultrasound frequency of 7 MHz the resultingattenuation would reach the undesirable range of 42 to 84 dB for a 6 cmthickness of breast tissue. FIG. 2-37 on page 34 of Stavros 2004 shows apenetration depth of around 3.5 cm for a breast ultrasound imageobtained at 12 MHz. Current commercially available FFBUs are believed tooperate in the range of ultrasound frequencies from 8 MHz to 14 MHz inorder to obtain acceptable image quality for the range of breast sizes.

The known current commercially available FFBU scanning devices arerectilinear scanners, with scanning lines essentially parallel to eachother as explained above. A significant challenge in these scanners istrying to fit a rectangular scan area over a round breast. Frequentlyeach breast has to be scanned two to five or more times in overlappingset of scans. Even with good image stitching techniques, such as “Rapidimage stitching and computer-aided detection for multipass automatedbreast ultrasound” reported by RF Change et al. (published in MedicalPhysics 2010; Vol. 37, pages 2063-2073), it is difficult to accuratelystitch several separate scans of a breast into one single set forming asingle image. Thus, a current practice of reading images of commercialFFBU is to view each of the several scans separately and independentlyas each scan covers different, although partially overlapping, parts ofthe breast. As a result, such multiple scans for each breast wouldrequire in longer interpretation times by physicians. Another problemfor such multiple scans is an increase in the time for each patient inthe scan examination room, which has a direct negative impact on: (1)patient throughput; and (2) revenue generation per FFBU per year.

There is a proposal for non-rectilinear FFBU scanning in WO 03/103500,which is not believed to have been commercially implemented. Thereference proposes the use of a cone-shaped tissue molding elementhaving a hole through which an ultrasonic transducer scans the breast asthe molding element rotates relative to the breast. The figure in thereference appears to show that the wall of the molding element convergesat an angle of about 90°. In comparison to one or more of the preferredembodiments described herein, where the scanned breast is flattenedagainst the patient's chest wall, using such a 90° molding element wouldmean scanning through a much greater thickness of breast tissue. Thiswould bring about two major shortcomings: (1) poorer image quality; and(2) limited range in size of breasts that can be scanned. This isbecause lower ultrasound frequency would have to be used for the greaterthickness of scanned breast tissue, particularly in the case of largerbreasts that would require ultrasound frequency below the minimumrecommended 7.5 MHz. Early FFBU developments involving laterallycompressed breasts (as in mammography), such as discussed in Pat. Publ.US 2006/0173303 A1, produced images of lower quality than currentdevices that scan a chestwardly compressed breast because lowerultrasound frequencies had to be used for larger breasts in such earlydevelopment FFBU devices, and resulted in a change-over to chestwardcompression. Additional issues arise in the rectilinear scanning devicesreferred to above and in the devices discussed in WO 03/103500, as wouldbe readily apparent to one skilled in the art in view of the disclosurein this patent specification,

SUMMARY

An apparatus and related methods for ultrasonically scanning a breastand displaying the volumetric information are provided, the apparatuscomprising an ultrasound transducer and a radial scanning template thatcompresses the breast in a generally chestward direction, the radialscanning template preferably being round and preferably having anopening in the center of the template through which the breast's nipplecan protrude. The radial scanning template has a slot-shaped openingextending generally radially outwardly from the center, through whichopening the ultrasound transducer scans the breast as the templaterotates over the breast. In one embodiment, the scanning template is“essentially planar,” which in this patent specification designates atemplate that may departs from absolute planarity only such that adifference between the levels of the central opening and the peripheryof the template is less than that for a template shaped as a truncatedcone that has a similar central opening and a sidewall that converges atan angle in the range of more than 175° to about 180°, in which case itcan be said that the template deviates from absolute planarity by anangle that is in a range of less than 2.5° to 0° and is called adeparture angle in this patent specification. In other embodiments thedeparture angle can be in the range of 5° to 0°, 10° to 0°, 15° to 0°,or 20° to 0°, depending on the length and shape of the transducer used.The template, if not absolutely planar, can be shaped substantially as ashallow truncated cone or it can be shaped like a shallow inverted bowl,and preferably has a generally central opening. The template's concaveside is configured to face and flatten a patient's breast chestwardly.The template preferably has a round circumference and may but need notbe circular. The inner (breast-facing) wall may curve in one or twodimensions. The template can be cam-shaped in outline, or close to ovalor even close to square or rectangular so long as it has a sufficientlyrounded corners to allow for rotation over a chestwardly compressedbreast as in the examples described below. The breast-facing side of theelongated ultrasound transducer that is used with the template canextend along a straight line or along a curved line so that a concavesurface would contact the breast, to better match the somewhat rounded,convex side of a breast flattened with the template. The edges of thebreast-facing side of the transducer and of the template and itsopenings preferably are sufficiently rounded or beveled to avoiduncomfortable contact of sharp edges or corners with the breast.

There are significant advantages in employing an essentially planarscanning template that can effectively flatten breast tissue against thechest wall and thereby reduce the required scan depth and makeconsistently possible and practical the use of higher ultrasoundfrequencies. The higher ultrasound frequencies (e.g., 8 MHz-15 MHz) thencan penetrate to the required depth and result in superior image qualityover images from lower ultrasound frequencies (e.g. below 7.5 MHz, whichwould be necessary for scans of thicker breast tissues in a mannerproposed in WO 03/103500). An essentially planar radial scanconfiguration also allows easier volumetric information reconstructionas well as display, which in turn provides ease in the interpretation ofdisplayed images by radiologists. Such scanning templates areparticularly effective for ultrasonically scanning the breast of asupine patient, although application to other patient positions (e.g.,prone, upright, decubitus) is within the scope of the preferredembodiments.

In one preferred embodiment, a hole in the center of the radial templateallows the nipple to protrude through the template during the scan. Thisovercomes image distortion and artifact problems of FFBU scanningdevices such as those proposed in U.S. Pat. No. 7,828,733 and in WO02/30287, which scan over the nipple during the scanning process andpush the nipple into the breast. WO 02/30287 recognizes the problem butproposes a different solution, namely, using a nipple pad in an effortto reduce the image distortion and artifact problem caused by scanningover the nipple. The hole in the center of the templates disclosed inthis patent specification also serves as a natural locator for thenipple, in contrast with the case of known scanning devices where healthprofessionals manually find the nipple in the image and mark itslocation in scanned images.

This radial scan configurations disclosed in this patent specificationare capable of covering a breast with a single scan by using a singletransducer, whereas a rectilinear scanning commercial FFBU, such as inU.S. Pat. No. 7,828,733, could cover a breast with 2 to 5 scans by usinga longer and thus more expensive transducer. Rectilinear scanning suchas in WO 02/30287 uses a greater number of scans to cover a breast,which makes reconstruction of 3D volumetric images more difficult due tobreast motion caused by the scanning process and due to image stitchingartifacts. Significant advantages of a single scan over multiple scansinclude: (1) reduced interpretation time; (2) increased patientthroughput; and (3) increased revenue generation for FFBU owners.According to some embodiments, image quality of a single scan device isfurther improved by slowing down the scan speed, which is not easilyaccomplished by current FFBUs when performing multiple scans withoutfurther reducing patient throughput.

Preferably, the radial scanning templates disclosed in this patentspecification comprise a material that is semi-rigid, or substantiallyrigid, that sufficiently flattens the breast chestwardly for scanningand is sufficiently optically translucent to facilitate visualizing thebreast for positioning and scanning.

According to one preferred embodiment, the ultrasound transducer is indirect contact with the breast skin through a slot-shaped opening in thetemplate. In another preferred embodiment, a fabric porous to anultrasound coupling agent such as gel extends across the slot-shapedopening in the template, and the ultrasound transducer scans the breastthrough the porous fabric. In still another preferred embodiment, atleast the inner side of the entire template is covered with a removablesock made of such a porous fabric. In yet another preferred embodiment,the patient wears a brassiere-shaped article where at least the portioncovering the breasts is made of such a porous fabric and may have holesthrough which the nipples protrude, and the templates described in thispatent specification are positioned over the fabric, with a nippleprotruding through a central hole in the template.

According to one preferred embodiment, a scanning template has only oneradially extending slot-shaped opening and only a single ultrasoundtransducer scans the breast. The radial scanning template rotatesthrough 360 degrees plus an overlap angle, if desired, during the breastultrasound scan, the overlap angle preferably being in a range of 5 to45°. Thus, breast tissue within the overlap angle is scanned twice. Theinformation from such dual scanning of some tissue can be used to reducepotential discontinuities in the resulting volumetric representation ofthe breast associated with the start-stop locations of the scan, usingsuitable blending of the duplicated scan information.

According to another preferred embodiment, different radial scanningtemplates and/or transducers, that have different sizes and shapes, areused to fit different sizes and shapes of the breasts to be scanned.

In still another preferred embodiment, a concavely curved transducer isused with a similarly concavely curved template.

According to another preferred embodiment, a plurality of ultrasoundtransducers and a corresponding plurality of slot-shaped openings in atemplate are provided. In general, where there are N transducers, a fullvolumetric scan can be achieved by rotating the radial scanning templateby 360/N degrees, plus an overlap angle, if desired, that can be lessthan 5° in the case of a sufficient number of transducers scanningconcurrently.

In one embodiment, at least two ultrasound transducers are used thathave different lengths corresponding to different centralhole-to-periphery distances around the radial scanning template. Eachultrasound transducer scans a different coronal sector of the breast. Inone example, a longer ultrasound transducers scans the coronal sector ofthe breast that is near the axilla, which sector usually extends fartherout from the nipple than other breast sectors, and a shorter ultrasoundtransducer scans other portions of the breast.

In one embodiment, the transducer is made of a single linear array oftransducer elements (sometimes referred to as 1D array). In anotherpreferred embodiment, the transducer is made of multiple arrays parallelto one another (sometimes referred to as 1.25D, 1.5D, 2D, etc. arrays).This type of multiple-arrayed transducers can provide better lateralspatial resolution than a single array transducer.

In one preferred embodiment, the nipple and sub-areola regions can bepartially covered with beam-steering of the scanning ultrasound beamfrom the transducer. In another embodiment, the nipple and sub-areolaregions can be separately scanned manually, for example with a handheldultrasound transducer.

The scan with a essentially planar radial template as disclosed in thispatent specification can generate a simpler set of images, which permitseasier and more accurate reconstruction and display of 3 D informationincluding, for example, coronal slice images. This scan configurationalso allows a cine review of original 2D images that facilitates imageinterpretation.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates in a perspective view a full-field breast ultrasound(FFBU) device.

FIG. 2 illustrates in a perspective exploded view an essentially planarscanning template and an ultrasound transducer for scanning achestwardly flattened breast.

FIG. 3 a is a top plan view of an essentially planar scanning template;FIG. 3 b is a cross-section through lines A-A′, and FIG. 3 c is across-section through lines B-B′. and 3 b are a plan view and across-sectional view, respectively, of an essentially planar scanningtemplate.

FIG. 4 a is a cross-sectional view illustrating a patient's breast thatis chestwardly compressed with an essentially planar template and isbeing scanned with an ultrasound transducer through a radially extendingopening in the template.

FIG. 4 b is a top view of the template of FIG. 4 a.

FIG. 4 c is a cross-sectional view a scanning template that is otherwisesimilar to the template of FIGS. 4 a and 4 b but departs from absoluteplanarity by a departure angle φ that is greater than 2.5°.

FIG. 5 is a plan view of a template with a membrane that is permeable toan ultrasound couplant such as a gel, through which an ultrasoundtransducer can scan the breast.

FIG. 6 is a cross-sectional view of the template of FIG. 5.

FIG. 7 is a cross-sectional view similar to FIG. 6 but additionallyillustrating a portion of a breast being scanned and a scanningultrasound transducer.

FIG. 8 is a top view of a template illustrating scan overlap angles.

FIG. 9 is a top view of a template having two radial slots for twoseparate ultrasound transducers, according to some embodiments.

FIG. 10 is a top view of a template that has a non-circular outline andmultiple radial slots through which respective transducers of differentsizes and/or other characteristics scan respective sectors of a breast.

FIG. 11 a illustrates a 3D scanned breast volume with coronal slices,according some embodiments.

FIG. 11 b illustrates a display of images of such coronal slices.

FIG. 12 a illustrates a 3D scanned breast volume and its relationshipwith original 2D scanned slices.

FIG. 12 b illustrates a display of a coronal slice and associatedorthogonal views of original 2D scans.

FIG. 12 c illustrates a display of a coronal slice with an abnormalityand of associated orthogonal views that contain the abnormality.

FIG. 13 a illustrate a cross-section of breast being scanned with anultrasound transducer that has a curved concave lower side and scansthrough an opening in a template that can be essentially planar orspherical or otherwise curved in two dimensions with a departure anglegreater than 2.5°.

FIGS. 13 b and 13 c illustrate side views of ultrasound transducersaccording to some embodiments.

FIG. 14 illustrates in block diagram form a system for acquiring andprocessing ultrasound images and displaying resulting processed imagesin cooperation with a user interface.

DETAILED DESCRIPTION

FIG. 1 illustrates a perspective view of a full-field breast ultrasound(FFBU) scanning apparatus 102 according to a preferred embodiment,comprising a frame 104 that may contain an ultrasound processor, amovable support arm 106, and a monitor 110 connected to the support arm106. FFBU scanning apparatus 102 further comprises an essentially planarradial scanning template 112 and an ultrasound transducer 114. Theradial scanning template 112 is configured to chestwardly compress abreast of a patient (e.g., a supine patient) while rotating around anaxis 122, preferably centered on the nipple hole 204. The ultrasoundtransducer 114 rotates with the radial scanning planar template 112 andscans the breast through a slot-shaped, radially extending openingtherein. For reference purposes herein, the +z direction refers to anoutward direction away from the patient's chest, the x-axis refers to aleft-right direction relative to the supine patient, and the y-axisrefers to a head-to-toe direction. The x-y plane thus corresponds to acoronal plane of a breast, the x-z plane corresponds to an axial plane,and the y-z plane corresponds to a sagittal plane.

Also illustrated in FIG. 1 is a rigid, two-pronged connector 116 and arigid, single-arm connector 120 that mechanically connect the radialscanning template 112 and the ultrasound transducer 114, respectively,to an actuator assembly 118 for achieving the movement functionalitiesdescribed herein. It should be understood that the mechanical elements116-120 in FIG. 1 are drawn by way of a conceptual example only and notto scale. In view of the disclosure in this patent specification, aperson skilled in the art would be readily able to construct the variousmechanical/electrical linkages, actuators, motors, sensors, etc.,required to achieve the described mechanical functionalities withoutundue experimentation. Accordingly, such mechanical/electrical detailsare mostly omitted from the drawings herein for clarity of description.

Preferably, support arm 106 is configured and adapted such that theoverall compression/scanning assembly 112-120 (i) is neutrally buoyantin space, or (ii) has a light net downward weight (e.g., 2-3 pounds) forbreast compression, while allowing for easy user manipulation.Optionally, the support arm 106, the template, and/or the transducer(s)can comprise potentiometers and/or other sensors (not shown) to allowforce, position, and/or orientation sensing for the overallcompression/scanning assembly 112-120, the template, and/or thetransducer(s). Other types of force, position, and/or orientationsensing (e.g., gyroscopic, magnetic, optical, radio frequency (RF)) canbe used instead or in addition.

Within frame 104 there can be provided a fully functional ultrasoundengine for driving one or more ultrasound transducers and generatingvolumetric breast ultrasound data and images from the scans inconjunction with the associated position and orientation information.The volumetric scan data can be transferred to one or more othercomputer systems for further processing using any of a variety of datatransfer methods known in the art. A general purpose computer, which canbe implemented on the same computer as the ultrasound engine, can beprovided for general user interfacing and system control. The generalpurpose computer can be a self-contained stand-alone unit, or can beremotely controlled, configured, and/or monitored by a remote stationconnected across a network.

FIGS. 2, 3 a, 3 b, and 3 c illustrate more detailed views of anessentially planar radial scanning template 112 in accordance with apreferred embodiment. Radial scanning template 112 preferably isrounded, e.g., has a generally circular shape, and defines therein aslot-shaped opening 202 that extends generally radially from a centralopening 204. The slot-shaped opening 202 is dimensioned to allow anultrasound transducer 114 to at least partially pass therethrough toscan the breast. Although shown as a one-dimensional array in FIG. 2,the ultrasound transducer 114 more generally can be multiple-arrayed(sometimes referred to as 1.25D, 1.5D, 2D, etc.), or hybridizationthereof without departing from the scope of the preferred embodiments.In one preferred embodiment, the FFBU scanning apparatus 102 is providedwith an interchangeable (and/or disposable) set of essentially planarradial scanning templates 112 that are differently sized or shaped fordifferently-sized or shaped breasts. In one example, eight (8) differentradial scanning templates having base diameters of 4 inches, 5 inches, 6inches, 7 inches, 8 inches, 9 inches, 10 inches and 12 inches areprovided. Exemplary diameters for the central opening 204 range betweenabout 0.25″ to 1″ (0.25 inches to 1 inch). The slot-shaped opening 202may have a width typically in the range of 0.25″ to 1″ depending on thesize of the ultrasound transducer to be inserted therethrough. Inaddition, a selection of templates can be provided that are notessentially planar but have greater departure angles.

In one preferred embodiment, the ultrasound transducer 114 is supportedand actuated independently of the radial scanning template 112. Inanother preferred embodiment, the ultrasound transducer 114 is integralwith, clipped to, or otherwise secured to or fused with or mounted onthe radial scanning template 112 for joint support and/or actuation.

With reference to FIG. 3 a, the essentially planar radial scanningtemplate 112 is shaped as a circular plate having a circular hole 204located at the center of the circular plate 304 and a radially extendingslot-shaped opening 202 from near the hole 204 to near the periphery ofplate 304. FIG. 3 b illustrates a sectional view along lines A-A′, andFIG. 3 c illustrates a sectional view along lines B-B.

In one preferred embodiment, the radial scanning template 112 is formedof a transparent or at least translucent material having mechanicalproperties similar to those of 40-mil thick polycarbonate plastic,40-mil polystyrene plastic, or a mechanically equivalent thickness ofpolyethylene terephthalate (PETE) plastic. In this embodiment, there issome amount of “give” or flexibility to the template 102, providing somedegree of comfort to the patient as well as adaptability todifferently-sized breasts while at the same time providing forsubstantial stabilization of the breast tissue for reliable volumetricimaging of the breast. Such a template is called “semi-rigid” in thispatent specification. In another preferred embodiment, the material fortemplate 102 comprises a transparent or at least translucent materialsuch as 140-mil thick glass, 140-mil acrylic, or 140-mil polycarbonateplastic. Such a template is called “rigid” in this patent specification.Preferably, a lower surface of the radial scanning template 112 makes aslippery contact with the skin surface in the presence of an ultrasoundcouplant such as gel between the template and the breast so thatrotation is easily achieved even when the breast is under some degree(e.g., 4-12 lbs.) of downward compression. Despite the slippery contactwith the breast, stabilization is provided by virtue of the generallycircular shape of the radial scanning template 112. Preferably, a curledlip, e.g., as illustrated in FIG. 3 b at 304 a, is provided around theperiphery 304 as well around the central hole 204 as illustrated at 204a, and a similar curled lip is provided at the edges of slot-shapedopening 202 as illustrated in FIG. 3 c at 202 a, to prevent skin cuts orchafing and provide additional comfort to the patient, similar to theway curled upper lips are provided on many paper, polystyrene, and PETEplastic drinking cups.

FIG. 4 a illustrates a side cut-away view of the essentially planarradial scanning template 112 as it chestwardly compresses a breast 404having a nipple 406. The view can correspond to the axial or sagittalplane, and also illustrates patient tissue 405 that surrounds breast 404laterally (e.g., in the coronal plane). The nipple 406 protrudes throughthe central opening 204. The transducer 114 scans the breast 404 throughthe slot-shaped opening 202. FIG. 4 b illustrates a top conceptual viewof FIG. 4 a.

FIG. 4 c illustrates a template 112 a that can be otherwise similar tothe essentially planar template 112 but has a conical surface thatdeparts from absolute planarity by a departure angle φ (phi) that isgreater than 2.5°. Rather than shaped as a truncated cone, template 112a can be shaped as a shallow inverted bowl with a side curving in twoorthogonal dimensions. A template with a departure angle φ greater than2.5° can be used, if desired, in place of each of the essentially planartemplates illustrated and discussed in this patent specification.

Whenever a departure angle is used that moves away from 0°, there is apenalty of scanning through increased breast thicknesses, which ismeasured as the distance from the scan surface to the chest wall. Forexample, if we define t (distance 480 in FIG. 4 c) as the maximumdifferential thickness increase from the scan surface to the chest wallsurface, then t could be expresses as the radial length of thetransducer L times the sine of the departure angle φ:

t=L sin φ

The following table shows the relationship:

TABLE 1 L = 3 inch L = 4 inch φ (degree) Sin φ t (cm) t (cm) 5 0.08720.7 0.9 10 0.1736 1.3 1.8 15 0.2588 2.0 2.6 20 0.3420 2.6 3.5 25 0.42263.2 4.3 30 0.5000 3.8 5.1At 10 MHz, according to D'Astous and Foster, an increase in 2.5 cm inscan depth would increase attenuation by 25 to 50 dB, which would have aserious negative impact on image quality. Unless in extraordinarycircumstances, either due to breast size or shape, where largerdeparture angles have to be used, for transducers having a radial lengthsmaller than three inches, one should preferably consider using adeparture angle of less than 30 degrees. For a three-inch transducer,one should preferably use a departure angle of less than 20 degrees. Fora four-inch transducer, one should preferably use a departure angle ofless than 15 degrees.

In the particular embodiment of FIGS. 4 a and 4 b, the slot-shapedopening 202 and the ultrasound transducer 114 both extend alongsubstantially the entire distance from the central nipple hole 204 tothe periphery of the radial scanning template such that a completevolumetric scan can be achieved in a single 360-degree rotation, withoptional beam-steering for facilitating sub-areola imaging. If desired,the rotation angle can be extended by a few degrees to achieve someoverlap of scanned breast tissue.

FIG. 5 illustrates a top view of a radial scanning template 502according to a preferred embodiment, comprising a central opening 504, aslot-shaped opening 506, and a membrane 510 extending across theslot-like opening 506. The ultrasound transducer (not shown in thisfigure) scans the breast through the membrane 510. The membrane 510preferably comprises a fabric material porous to ultrasound couplingagent such as gel, which can be advantageous in that air bubbles arereduced. As used in this patent specification, fabric refers generallyto a material structure of interconnected or interleaved parts, such ascan be formed by knitting, weaving, or felting natural or syntheticfibers, assembling natural or synthetic fibers together into aninterlocking arrangement, fusing thermoplastic fibers, or bondingnatural or synthetic fibers together with a cementing medium, andfurther refers to materials having similar textures or qualities asthose formed thereby, such as animal membranes or other naturallyoccurring substances having fabric-like properties (either inherently orby processing), and such as materials generated by chemical processesyielding fabric-like webbings. One particularly suitable material forthe taut fabric sheet comprises a polyester organza material having afilament diameter of about 40 microns and a filament spacing of about500 microns. However, the fabric membrane may comprise any of a varietyof other fabrics that are substantially inelastic and generally porousto ultrasound couplants without departing from the scope of the presentteachings. Examples include, but are not limited to, polyester chiffonfabrics and cloth fabrics comprising straight weaves of substantiallyinelastic fibers. If the weave is particularly tight, for example, as incloth used in men's dress shirts or in many bed sheets, porosity can beachieved by additional treatment. The additional treatment can involveforming an array of perforations in the cloth or otherwise introducingirregularities that allow the ultrasound couplant to soak or seepthrough.

FIG. 6 illustrates a cross-sectional view of an essentially planarradial scanning template 602 according to a preferred embodiment,comprising a central opening 604, a slot-shaped opening 606, and aporous fabric membrane 610 in the form of a stretchable, generallycircular fabric sock extending over the entire bottom-side of the planartemplate 602 (i.e., the side that faces and contacts the patient'sbreast) and across the slot-shaped opening 606 but preferably with acentral hole 614 in the membrane for the nipple to protrude through. Thesock can but need not extend over some or all of the upper side oftemplate 602. According to another preferred embodiment, the porousfabric sock can be mounted on a circular or round frame that is snappedon or otherwise secured to the substantially planar radial scanningtemplate 602. The ultrasound transducer (not shown in this figure) scansthe breast through the porous fabric membrane 610 wetted with anacoustic coupler such as gel.

FIG. 7 illustrates a side view section of an essentially planar radialscanning template 702 according to a preferred embodiment, comprising acentral opening 704, and a slot-shaped opening 706. The radial scanningtemplate 702 is positioned over a patient (not shown except for aportion of the breast 720) wearing a brassiere-shaped article 710comprising a porous membrane such as fabric at least over the breast andpreferably with a central hole 714 for the nipple 730 to protrudethrough. The ultrasound transducer 114 scans the breast through theporous fabric article 710.

FIG. 8 illustrates a top view of a radial scanning template 802according to a preferred embodiment, comprising a single slot-shapedopening 804 corresponding to a single ultrasound transducer (not shownin this figure). The radial scanning template is preferably rotated 360°plus an overlap angle “a” (alpha) during the breast ultrasound scan, theoverlap angle preferably being in a range, if desired, of 5° to 45°. Thecoronal sector associated with the overlap angle alpha (i.e., thepie-shaped sector of the compressed breast subtending the arc betweenradial lines 822 and 824 in FIG. 8) is thus imaged twice. The dualvolumetric images for the overlap sector can be advantageously used toreduce discontinuity artifacts in the volumetric representation of thebreast that might otherwise occur along the radial line 822. In onepreferred embodiment, the dual volumetric images are arithmeticallyaveraged for smoothing over the discontinuity. However, more advancedstitching techniques can be used. Other mathematical methods forprocessing the dual volumetric images for reducing discontinuityartifacts exist and are within the scope of the preferred embodiments.One non-limiting example is weighted averaging in which the weightsapplied to one of the images of the overlap gradually decrease fromunity to zero from the start to the end of the overlap zone while theweights applied to the other image in the overlap zone graduallyincrease from zero to unity. For example, the weights applied to theimage obtained at the start of the circular scan increase with angulardistance from line 822.

FIG. 9 illustrates a top view of a radial scanning template 902according to a preferred embodiment, comprising two slot-shaped openings904 and 906 corresponding to two ultrasound transducers (not shown) usedduring a scan. In one preferred embodiment, the radial scanning template902 is preferably rotated by 180° plus, if desired, an overlap angleduring the breast ultrasound scan, thereby reducing scanning time ascompared to the use of a single ultrasound transducer. The image datafrom the two transducers is processed through stitching or othercompeting algorithms into a volumetric image of the breast.

In another preferred embodiment, the radial scanning template 902 isrotated through the full 360°, plus an overlap angle if desired, withthe different ultrasound transducers being differently configured withrespect to at least one imaging parameter. The resultant volumetricscans are then compounded or composited in any of a variety ofadvantageous ways, with or without different weighing, and/or can beviewed a separate images. Parameters that can be varied among thetransducers include, but are not limited to, scan frequency, tilt angle,elevation beamwidth, scan mode (e.g., B-mode, harmonic, Doppler,elastography), in-plane acoustic interrogation angles, and differentin-plane multi-angle compounding schemes. It should be apparent to aperson of ordinary skill in the art after having read this patentspecification to expand this scan configuration using 2 transducers to ascan configuration using a greater number of transducers.

FIG. 10 illustrates a top view of a radial scanning template 1002according to a preferred embodiment, comprising five slot-shapedopenings 1004, 1006, 1008, 1010, and 1012 corresponding to fiveultrasound transducers (not shown in this figure), each scanning thebreast through a respective one of the openings directly or through amembrane (fabric) as described for an individual transducer in otherembodiments. According to the preferred embodiment of FIG. 10, at leasttwo of the ultrasound transducers have different radial lengthscorresponding to different distances from the central nipple hole to theperiphery of the radial scanning planar template. Each ultrasoundtransducer scans a different coronal sector of the breast. In theexample of FIG. 10, which is for the left breast of a supine patient,the longest ultrasound transducer 1006 scans the coronal sector nearestthe axilla, while the shortest ultrasound transducer 1012 scans aninferior medial sector of the breast. Accordingly, it can be appreciatedthat the general shape of a radial scan template according to thepreferred embodiments is not limited to circular shapes with nippleopenings at the geometric center, but rather includes different shapesand different locations of the nipple opening relative to the template'sradial periphery. Likewise, a radial scan template according to thepreferred embodiments is not limited to a circular shape, but rather canhave a differently shaped periphery (e.g., oblong, elliptical,cam-shaped).

The obtained ultrasound scans can be advantageously used in a variety ofways in accordance with the preferred embodiments. For example, it hasbeen found that the acquired volumetric data is particularlyadvantageous for generating coronal slice images of the breast as shownin FIG. 11 a, each preferably representing a slice that has a selectedthickness in the z-direction (i.e., a direction toward or away from thepatient's chest wall), although images of slices that have otherorientations and may differ in thickness from each other also are withthe scope of this patent specification. The slice thickness preferablyis in the range of 0.5-2.0 mm, but can be in the range of 0.1-1.5 mm, or0.1-2.0 mm, or 0.1-10.0 mm, and even a greater range. Another advantageof displaying coronal images is that they show lesion spiculations verywell, which are an easily recognizable feature of a cancerous lesion.

FIGS. 11 a and 11 b illustrate a 3D image 1101 of the breast representedas slices 1110-1120 reconstructed from 2D radial scan images such asimage 1106, and the display of slice images 1110-1120 of slices of the3D image. The 3D image 1101 is reconstructed from a great number oforiginal 2D images from the radial scan that are transverse to thecoronal plane. One such original 2D image 1106 is shown. Also shown isthe central nipple hole 1104. The 3D image 1101 can be considered asdivided into images of coronal slices of the breast (slicesperpendicular to z-axis) 1110, 1112, 1114, 1116, 1118, 1120, etc.,computed from the volumetric stack 1101 as known the ultrasound imagingtechnology. FIG. 11 b illustrates an example of how the slice images canbe displayed to the physician or other health professional forinterpretation. The last (bottom) slice 1120 is usually the slice at thechest wall or rib cage (which generally would show ribs 1122, 1123,1124, etc. to confirm that adequate breast penetration has beenachieved). The nipple and sub-areola regions, obtained either throughbeam-steering or manual scanning with a handheld transducer or otherwisecan be displayed in stitched images or separately.

FIGS. 12 a and 12 b illustrate a single coronal slice image 1210 in avolumetric 3D image or stack 1201 of breast tissue, and a display of theslice image and of 2D images. Two original 2D radial scan images 1206and 1208 bisect the 3D image, for example in a sagittal plane, and arespaced 180° from each other. The central nipple hole 1204 is also shown.FIG. 12 b illustrates a display of 2D images 1206 and 1208 together witha display of 2D images 1236 and 1238 are a pair orthogonal to the pair1206 and 1208 (e.g., if the pair 1206-1208 are sagittal images than thepair 1236-1238 are axial images). Chest wall line 1209 is also shown.Notably, in this example the two orthogonal pairs of images are original2D radial scan images, unlike similar pairs in known commerciallyavailable FFBUs, where orthogonal pairs are believed to be constructedfrom a volumetric reconstructed 3D image stack and consequently havereduced image quality. Typically, the reader would perform a quickreview of coronal slices as shown in FIG. 11 b, and/or perform a cine orother review of the coronal image in FIG. 12 b, and/or a quick cine orother review of the original 2D images in FIG. 12 b. A preferred way toperform a cine review of the original 2D images is simply to rotate thecoronal slice 1210 to view the 180° pairs. Rotation of the coronal slicecan be done with a control knob, by a cine review control, or by anotherinterface, while other information such as the rotational angle, left orright breast, patient position, etc. are also displayed (not shown inFIG. 12 b).

During the viewing of a coronal slice, an abnormality may be noted. Asillustrated in FIG. 12 c, when an abnormality 1250 in the coronal sliceis found, with a click on the abnormality 1250 with a mouse orcontroller or by some other input, corresponding abnormality 1251 in theoriginal 2D radial scan containing this abnormality can then beautomatically pulled up and displayed through suitable algorithmsprogrammed in frame 104 as known in ultrasound image processingtechnology. Similarly, a constructed orthogonal 2D image 1240 containingthis abnormality 1252 can also be shown simultaneously. Also visible inconstructed image 1240 is chestwall 1241.

FIG. 13 a illustrates the use of an ultrasound transducer 1314 that hasa concavely curved bottom 1314 a facing and scanning a patient's breast1304 that is compressed with a rotating, concavely shaped template 1312having a central opening through which the nipple 1305 protrudes. Whiletemplate 1312 is illustrated as compoundly concavely curved, it can beplanar or spherical in shape, and transducer 1314 can still have asimilar concavely curved lower side 1314 a, or it can have a generallyplanar lower side. In embodiments where several transducers concurrentlyscan a breast, e.g., as in FIG. 10, each transducer can have a concavelower side or some of the transducers (e.g., the shortest transducer(s))can have straight lower sides, or all can have straight lower sides. Incases where the template 1312 is spherical such as shown in FIG. 13 a,the departure angle φ can be greater than 2.5°, but preferably would notexceed about 20° as shown. FIG. 13 b illustrates a side view oftransducer 1314 having a curved lower side 1314 a in a radial plane, buta straight lateral lower side. FIG. 13 c illustrates a side view of amulti-array transducer 1314 c, according to some embodiments. Themulti-array transducer 1314 c is wider as shown. Additionally, the lowercurved side 1314 d can be concavely curved both in the radial and in thelateral dimensions to match a concavely curved template 1312.

FIG. 14 illustrates in block-diagram form certain computer-implementedfacilities for carrying out scanning and image processing and displayaccording to embodiments described above. One or more ultrasoundtransducers 1402 scanning the breast as described above supply raw 2Dultrasound images to a pre-processing facility 1404 that applies variousalgorithms to the raw images as known in the pertinent technology togenerate pre-processed 2D images each representing a planar section ofthe breast conforming to a plane extending in the chestward direction(transverse to the coronal plane). These pre-processed 2D images aresupplied to a facility 1406 that reconstructs from them a 3D image ofthe breast and, if the 3D image is in a form different from a stack ofcoronal slice images representing breast slices of selected thicknesses(e.g., as a non-limiting example, slices that are 0.5-10 mm thick) thefacility generates such slice images from the 3D image of the breast.Thus far, the operation is similar to the known generation of 2D and 3Dimages and slice images in commercially available FFBU devices, exceptthat the raw 2D images are generated using the essentially planartemplate described above. A display facility 1408 receives thepre-processed 2D images from facility 1404 and the 3D image and/or thecoronal slice images from reconstruction facility 1406. The displayfacility 1408 includes one or more computer display screens andcomputerized processing circuits and software, and operates under thecontrol of a user interface 1410 to generate and display slice imagessuch as 1110 through 1120 as illustrated in FIGS. 11 a and 11 b and/or aslice image such as 1210 together with pairs of pre-processed 2D imagessuch as 1206-1208 and 1236-1238 illustrated in FIGS. 12 a and 12 b. Thecoronal slice images of FIG. 11 b can be displayed concurrently or insequence or in a cine mode. Per operator control through interface 1410,the images can be moved on the display screen or superimposed or one ormore can be changed, such as by changing the orientation of the slicethat the image represents, or the thickness of the slice, or thetransparency of one or more superimposed images, or the type ofprojection that generated the slice (e.g., minimum or maximum intensityprojection) by applying image processing techniques known in theultrasound imaging field and/or in other image processing and displayfields such as post-production of still or video images. Similarly, theimages illustrated in FIG. 12 b can be displayed in the illustratedformat or in other formats known in the pertinent technology. Asnon-limiting examples, the slice image 1210 of FIG. 12 b can be changedto represent a slice that has a different orientation or thickness or toan image of the slice that was generated in a different way (e.g., by adifferent type of projection), and the 2D images or FIG. 12 b also canbe varied under control of inputs from interface 1410, such as byrotating their planes around an axis normal or only transverse to thecoronal plane, by changing the angle between the planes of the two pairsof the 2D images, by changing the range of pixel values in the images(i.e., by controlling the window width of the images), and in other waysknown in the technology of displaying pixel value images. Some or all ofthe facilities illustrated in FIG. 14 can be implemented by programmingthe computing equipment in frame 104 or FIG. 1, or by carrying outprocessing in a separate computer equipment connected thereto, or in aworkstation that is remote from frame 104 but is coupled therewith toreceive the 2D images that the transducer(s) generate. The softwarecontrolling the operation of the equipment illustrated in FIGS. 1 and 14can be stored in non-transitory form in computer-readable media to forma program product.

According to some embodiments, images from prior examinations could alsobe shown together with the images of the current examination of apatient using display facility 1408 to view changes over time. Accordingto some embodiments, an image that represents the difference over timebetween the images is displayed using display facility 1408. Accordingto yet other embodiments, CAD (computer aided detection and diagnosis)results and/or other image enhancing results can also be displayed usingdisplay facility 1408.

Whereas many alterations and modifications of the examples describedabove will no doubt become apparent to a person of ordinary skill in theart after having read the foregoing description, it is to be understoodthat the particular embodiments shown and described by way ofillustration are in no way intended to be considered limiting. By way ofexample, it is to be appreciated that any of a variety of differentframe assemblies can be used that position, compress, rotate, andotherwise manipulate the scanning template, whether the scanningtemplate is permanently used and re-used for different patients or isdisposable for each patient, without departing from the scope of thepresent teachings. Moreover, in one or more alternative preferredembodiments, the basic profile of the radial scanning template can beelliptically shaped, etc., rather than strictly circular-shaped asindicated in some of the attached drawings. The scanning surface of theultrasound transducer can be arched or make to conform to another curvedsurface in a similar manner, if desired. Therefore, references to thedetails of the embodiments are not intended to limit their scope.

What is claimed is:
 1. An apparatus for ultrasonically scanning abreast, comprising: an essentially planar radial scanning templateconfigured to contact and compress the breast chestwardly, wherein thetemplate has a rounded periphery and a nipple hole configured for abreast nipple to protrude therethrough, and the template has one or moreelongated, slot-shaped openings extending from the central hole toward aperiphery of the template; one or more elongated ultrasound transducerseach aligned with a respective one of the one or more slot-shapedopenings; said template being configured to rotate over the breast whilecompressing the breast, and said one or more transducers beingconfigured to rotate with the template to scan the breast ultrasonicallythrough the respective one or more slot-shaped openings and to generate2D ultrasound images of the breast; and a computer-implemented imageprocessing and display facility associated with the one or moretransducers and configured to receive and process the 2D images intoimages of slices of the breast that have selected thicknesses andorientations, and further configured to display, under operator control,at least one or more images selected from the slice images.
 2. Theapparatus of claim 1 in which the image processing and display facilityis configured to display one or more images selected from the 2D imagesconcurrently with the display of one or more images selected from theslice images.
 3. The apparatus of claim 1 in which the image processingand display facility is configured to concurrently display a first 2Dimage and a second 2D image, both of which are selected from the 2Dimages such that the first and second 2D images are 180 degrees apart.4. The apparatus of claim 1 in which the template includes two or moreslot-shaped openings and two or more ultrasound transducers each alignedwith a respective one of the openings.
 5. The apparatus of claim 4 inwhich two or more of the ultrasound transducers differ from each otherin radial length.
 6. The apparatus of claim 4 in which two or more ofthe ultrasound transducers differ from each other in characteristics inaddition to any differences in radial length.
 7. The apparatus of claim4 in which the template has a non-circular shape and is configured tohave greater radial dimension in a sector configured to approach anaxilla of a patient when the patient's breast is being scanned with thetransducers.
 8. The apparatus of claim 1 in which edges of the templateare provided with rounded lips to avoid contact of sharp edges withpatient skin.
 9. The apparatus of claim 8 in which said rounded edgesinclude edges at a periphery of the template and at the one or moreopenings in the template.
 10. The apparatus of claim 1 in which at leastone of the one or more transducers has an underside configured tocontact the breast with a concave surface.
 11. The apparatus of claim 1in which the template is configured to scan the breast with one or moretransducers over a scan angle that exceeds 360° by an overlap angle. 12.The apparatus of claim 11 in which the template is configured to scanthrough an overlap angle that is in the range of 5°-45°.
 13. Theapparatus of claim 1 including a membrane permeable to an acousticcouplant that extends across at least one of the one of more slot-shapedopenings, and wherein at least one of the one or more ultrasoundtransducers scans the breast through the membrane.
 14. An apparatus forultrasonically scanning a breast, comprising: a radial scanning templateconfigured to contact and compress the breast chestwardly with a concaveinner surface having a departure angle less than 20°, wherein thetemplate has a rounded periphery and a nipple hole configured for abreast nipple to protrude therethrough, and the template has one or moreelongated, slot-shaped openings extending from the central hole toward aperiphery of the template; one or more elongated ultrasound transducerseach aligned with a respective one of the one or more slot-shapedopenings; said template being configured to rotate over the breast whilecompressing the breast, and said one or more transducers beingconfigured to rotate with the template to scan the breast ultrasonicallythrough the respective one or more slot-shaped openings and to generate2D ultrasound images of the breast; and a computer-implemented imageprocessing and display facility associated with the one or moretransducers and configured to receive and process the 2D images intoimages of slices of the breast that have selected thicknesses andorientations, and further configured to display, under operator control,at least one or more images selected from the slice images.
 15. Theapparatus of claim 14 in which the image processing and display facilityis configured to display one or more images selected from the 2D imagesconcurrently with the display of one or more images selected from theslice images.
 16. The apparatus of claim 14 in which the imageprocessing and display facility is configured to concurrently display afirst 2D image and a second 2D image, both of which are selected fromthe 2D images such that the first and second 2D images are 180 degreesapart.
 17. The apparatus of claim 14 in which the template includes twoor more slot-shaped openings and two or more ultrasound transducers eachaligned with a respective one of the openings.
 18. The apparatus ofclaim 17 in which two or more of the ultrasound transducers differ fromeach other in radial length.
 19. The apparatus of claim 17 in which twoor more of the ultrasound transducers differ from each other incharacteristics in addition to any differences in radial length.
 20. Theapparatus of claim 17 in which the template has a non-circular shape andis configured to have greater radial dimension in a sector configured toapproach an axilla of a patient when the patient's breast is beingscanned with the transducers.
 21. The apparatus of claim 14 in whichedges of the template are provided with rounded lips to avoid contact ofsharp edges with patient skin.
 22. The apparatus of claim 21 in whichsaid rounded edges include edges at a periphery of the template and atthe openings in the template.
 23. The apparatus of claim 14 in which atleast one of the one or more transducers has an underside configured tocontact the breast with a concave surface.
 24. The apparatus of claim 14in which the template has a departure angle of less than 15°.
 25. Theapparatus of claim 14 in which the template has a departure angle ofless than 10°.
 26. The apparatus of claim 14 in which the template has adeparture angle of less than 5°.
 27. The apparatus of claim 14 includinga membrane that is permeable to an acoustic couplant and through whichat least one of the one or more transducers scans the breast.
 28. Amethod of ultrasonically scanning a patient's breast comprising:chestwardly compressing the breast with a radial scanning templateconfigured to contact and compress the breast chestwardly with a concaveinner surface having a departure angle less than 20°, wherein thetemplate has a rounded periphery and a nipple hole configured for abreast nipple to protrude therethrough, and the template has one or moreelongated, slot-shaped openings extending from the central hole toward aperiphery of the template; ultrasonically scanning the chestwardlycompressed breast with one or more elongated ultrasound transducers eachaligned with a respective one of the one or more slot-shaped openingswhile the template and the transducers rotate over the breast;generating 2D ultrasound images of the breast from signals provided bythe scanning one of more transducers; computer-processing the 2D imagesinto images of slices of the breast that have selected thicknesses andorientations; and displaying under operator control at least one or moreimages selected from the slice images.
 29. The method of claim 28 inwhich the compressing step comprises compressing the breast with anessentially planar radial scanning template.
 30. The method of claim 28including interposing a membrane that is permeable to an acousticcouplant between the breast and the one of more transducers during saidscanning of the breast.
 31. The method of claim 30 including interposinga membrane that is permeable to an acoustic couplant between the side ofthe template and the breast during said scanning.
 32. An apparatus forultrasonically scanning a breast, comprising: a concavely curved radialscanning template configured to contact and compress the breastchestwardly, wherein the template has a rounded periphery and a nipplehole configured for a breast nipple to protrude therethrough, and thetemplate has one or more elongated, slot-shaped openings extending fromthe central hole toward a periphery of the template; one or moreelongated ultrasound transducers each aligned with a respective one ofthe one or more slot-shaped openings and each having a lower surfacethat is shaped to correspond to the concavely curved radial scanningtemplate; said template being configured to rotate over the breast whilecompressing the breast, and said one or more transducers beingconfigured to rotate with the template to scan the breast ultrasonicallythrough the respective one or more slot-shaped openings and to generate2D ultrasound images of the breast; and a computer-implemented imageprocessing and display facility associated with the one or moretransducers and configured to receive and process the 2D images intoimages of slices of the breast that have selected thicknesses andorientations, and further configured to display, under operator control,at least one or more images selected from the slice images.
 33. Theapparatus of claim 32 in which the image processing and display facilityis configured to display one or more images selected from the 2D imagesconcurrently with the display of one or more images selected from theslice images.
 34. The apparatus of claim 32 in which the imageprocessing and display facility is configured to concurrently display afirst 2D image and a second 2D image, both of which are selected fromthe 2D images such that the first and second 2D images are 180 degreesapart.
 35. The apparatus of claim 32 in which the template includes twoor more slot-shaped openings and two or more ultrasound transducers eachaligned with a respective one of the openings.
 36. The apparatus ofclaim 32 in which the template has a departure angle of less than 45°.37. The apparatus of claim 32 in which the template has a departureangle of less than 30°.
 38. The apparatus of claim 32 in which thetemplate has a departure angle of less than 15°.
 39. The apparatus ofclaim 32 including a membrane permeable to an acoustic couplant thatextends across at least one of the one of more slot-shaped openings, andwherein at least one of the one or more ultrasound transducers scans thebreast through the membrane.
 40. The apparatus of claim 32 wherein saidlower surface of each of the one or more transducers is concavely curvedalong both a longitudinal direction of the lower surface and a directionorthogonal to the longitudinal direction.
 41. The apparatus of claim 40wherein at least one of the one or more transducers includes multipletransducer arrays parallel to one another.